In many residential toilets, a volume of water is stored in a water tank located above the toilet. When the toilet is flushed, gravity moves the water from the water tank into the toilet bowl and, from there, through a waste outlet connected to a sewer pipe. Toilets of this type may use between 1.6 and 5 gallons of water per flush.
In many commercial and institutional toilets, generally referred to as “blowout” toilets, the aforementioned water tank is eliminated in favor of a flush valve, generally referred to as a “flushometer”, which directs pressurized water from a water supply line into upper and lower portions of the bowl. In toilets of this type, the volume of water needed to close, or reset, the flushometer, and the volume of water needed to reseal the bowl against migrating sewer gas, establish a minimum amount of water needed to accomplish each flush.
More specifically, the flushometer delivers a predetermined, metered amount of pressurized water to the bowl so as to use less water while providing at least the same flushing effectiveness as the conventional residential toilet which uses the force of gravity to deliver water into the bowl. Within the flushometer, a diaphragm or piston separates upper and lower chambers. When the flushometer is actuated, the diaphragm or piston is lifted from its seat, which allows water to flow. A small amount of the flowing water is diverted into the upper chamber to eventually reseat the diaphragm or piston and thereby reset the flushometer for the next flush. Thus, while the flushometer is mechanically or electronically actuated in response to an actuation action or signal, it is reset substantially automatically by the action of the water flowing through it. The minimum amount of water that must be diverted to reseat the diaphragm or piston and thereby reset the flushometer establishes the minimum amount of water that must flow through the flushometer and into the bowl during flushing.
Furthermore, the waste outlet from the bowl is connected directly to a sewer line. The water maintained in the bowl between flushings covers and seals the outlet. If the water level is not sufficient to fully cover and seal the outlet, then sewer gas in the sewer line can migrate into the bowl. Thus, the minimum amount of water needed to cover and seal the outlet further establishes the minimum amount of water that must flow into the bowl during flushing.
Available blowout toilets use 1.6 gallons or more per flush cycle, with, for example, 0.85 gallons being used to flush waste from the bowl, and the remaining 0.75 gallons being used to cover and seal the outlet. Using any less water would likely either adversely affect the proper functioning of the flushometer or fail to cover and seal the outlet.